Add JS serialization

[Pfeil]

Later validation features could make use of a JS serialization so we can calculate the records for the example documents within the browser. We can do so by generating a JS version of the code we currently generate for python and then execute it in the browser directly. This can be useful to understand the design better and do basic, practical checks and would also enable us to export JS in addition to python.

Differences to the python code as we have it now

• no Typed PID Maker invocation required
• no project management required

[Pfeil]

I think this is getting a higher priority soon. It is the basis for more interactive testing and verification, but especially for a new milestone which we will define in january. It will involve directly mapping to records, creating some HTML representation, and possibly an upload button. More on that later.